Curable organic polymer comprising at least one acylurea unit, its preparation and use

ABSTRACT

Moreover, the present invention suggests a process for the preparation of said polymer and the use of said curable organic polymer for the preparation of a cured composition and for the preparation of hydroxyurethanes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/507,299 filed on Feb. 28, 2017, which is a national stage applicationof International Application No. PCT/EP2015/066837, filed Jul. 23, 2015,which claims priority from European Patent Application No. 14185105.5,filed Sep. 17, 2014, which applications are incorporated herein byreference.

The present invention relates to a curable organic polymer comprising atleast one acylurea unit represented by structural formula (I):

Moreover, the present invention relates to a process for the preparationof said polymer and to the use of said curable organic polymer for thepreparation of a cured composition and for the preparation ofhydroxyurethanes.

Polyurethanes based on polyisocyanates belong to the prior art. Theseare used for example as adhesives, sealants, casting compositions, ascorrosion protection and for coatings. The high resistance to acids,alkalis and chemicals of the cured compositions obtained in this way areadvantageous. However, monomeric low molecular weight (poly)isocyanatecompounds are toxicologically unacceptable, especially if they arereadily volatile or migrate. This holds especially true for applicationby the final customer.

Polyurethane systems can also be obtained starting from cyclic carbonatecompounds, which are toxicologically acceptable. Thus, e.g. glycerolcarbonate (4-(hydroxymethyl)-2-oxo-1,3-dioxolane) is regularly used incosmetics.

WO 2011/157551 A1 discloses 2-oxo-1,3-dioxolane-4-carboxylic acid andesters thereof according to formula (V):

wherein R₁ represents a group selected from straight-chain or branchedaliphatic groups, aryl groups, aralkyl groups and alkylaryl groups, andis preferably methyl or ethyl. Moreover, R₁ can be an n-valent radical,which may be substituted with at most n-1 further2-oxo-1,3-dioxolane-4-carboxylic groups of formula (Va):

The afore mentioned esters may be cured with amine hardeners to formhydroxyurethanes. However, WO 2011/157551 A1 neither discloses norsuggests the curable organic polymer of the present invention, nor itspreparation and use.

WO 2013/092011 A1 discloses 2-oxo-1,3-dioxolane-4-carboxamides offormula (VI):

wherein R₁ and R₂, in each case independently of one another, areselected from H, straight-chain, branched or cyclic C₁₋₁₂-alkyl groups,C₆₋₁₀-aryl groups, C₆₋₁₂-aralkyl groups and C₆₋₁₂-alkaryl groups or,together with the N atom to which they are bonded, form a 5- to8-membered ring, and R₃ is selected from H and straight-chain, branchedor cyclic C₁₋₁₂-alkyl groups, or R₁ and R₃ are each H, and R₂ is ann-valent radical, wherein n is an integer greater than 1, preferably2-5, in particular 2-3, which is substituted with n-1 further2-oxo-1,3-dioxolane-4-carboxamide groups of formula (VIa):

These 2-oxo-1,3-dioxolane-4-carboxamides, wherein R₂ is substituted, areaccessible inter alia through reaction of2-oxo-1,3-dioxolane-4-carboxylic acid with polyisocyanates, e.g.:

and can also be cured with amine hardeners to form hydroxyurethanes,e.g.:

However, the carboxamide-based systems prepared from2-oxo-1,3-dioxolane-4-carboxylic acid and polyisocyanates exhibit alimited number of crosslinkable cyclic carbonate groups depending on thefunctionality of the polyisocyanates. Commercial polyisocyanates with afunctionality higher than 3, i.e. more than 3 isocyanate groups permolecule, are rare and suffer from very high viscosity and thus lowworkability.

EP 14 158 345.0 filed on Mar. 7, 2014, discloses 2-hydroxyethyl2-oxo-1,3-dioxolane-4-carboxylates of formula (VII):

wherein one of R₁ and R₂ can be hydrogen. In particular, R₁ and R₂, ifnot hydrogen, and in each case independently of one another, areselected from straight-chain, branched or cyclic C₁₋₂₂-alkyl groups,preferably C₁₋₁₂-alkyl groups, C₆₋₁₂-aryl groups, C₆₋₁₈-aralkyl groupsand C₆₋₁₈-alkaryl groups, wherein R₁ and/or R₂, in each caseindependently of one another, may comprise at least one additionalfunctional group, selected from hydroxyl groups, ether groups, estergroups, epoxy groups, and double bonds, and wherein R₂ may besubstituted with up to 10, preferably with 1 to 5, and in particularwith 1 or 2 further 2-hydroxyethyl 2-oxo-1,3-dioxolane-4-carboxylicgroups of formula (VIIa):

wherein R₁ has the above meaning.

These 2-hydroxyethyl 2-oxo-1,3-dioxolane-4-carboxylates, wherein R₁ issubstituted, are accessible inter alia through reaction of2-oxo-1,3-dioxolane-4-carboxylic acid with polyepoxides, e.g.:

and can also be cured with amine hardeners to form hydroxyurethanes.

However, the 2-hydroxyethyl 2-oxo-1,3-dioxolane-4-carboxylate basedsystems prepared from 2-oxo-1,3-dioxolane-4-carboxylic acid and(poly)epoxides often suffer from poor curing behavior due to cleavage ofthe present ester groups by the amine hardener.

In summary, binders prepared according to the prior art usually bear 2to 3 cyclocarbonate groups which can be reacted with amines to achievecrosslinking/curing. Thus, the crosslinking density is quite low andmainly soft and elastic cured materials are obtained.

It was thus the object of the present invention to essentially avoid atleast some of the disadvantages of the prior art as described above. Ingeneral terms, the aim was to provide a 2-oxo-1,3-dioxolane-based systemwhich is toxicologically acceptable, readily accessible, highly reactivewith amine hardeners and is suitable as a preferably low-viscous, highlycrosslinkable cyclocarbonate-functional binder. In order to obtain ahigh crosslinking density of the cured product and thus good mechanicaland chemical properties, a high density of crosslinkable groups (f≥3)within the curable polymer (resin) was required. Both, working with(poly)isocyanates and the presence of amine-labile ester groups in thecurable molecule should be avoided.

These objects have been achieved with the features of the independentclaims. The dependent claims relate to preferred embodiments.

It was surprisingly found that suitable cyclocarbonate-functionalbinders with a plurality of crosslinkable groups can be prepared in anaddition reaction between a carbodiimide and2-oxo-1,3-dioxolane-4-carboxylic acid of formula (III) (here called“CYCA”). With this approach, every diimide (resin) can be easilyconverted into a curable polymer containing2-oxo-1,3-dioxolane-functional acylurea units. The resulting binders areoften stable and soluble in water which allows good workability and aVOC-free dosage form. Moreover, they can be cured with amines to givehydroxypolyurethanes with good chemical and mechanical properties and ahigh crosslinking density.

U.S. Pat. No. 4,328,138 describes curable acylurea polymers and coatingcompositions which cure by reaction of ethylenic unsaturation of theacyl group. The subject polymers are prepared by reaction of a polymericcarbodiimide with an ethylenically unsaturated monocarboxylic acid.Neither cyclic carbonates nor curing with amine hardeners and thepreparation of hydroxyurethanes are mentioned or suggested.

DE 2714293 A1 describes polyhydroxyl compounds containing acyl ureagroups useful in preparation of polyurethane foams. Examples forsuitable carboxylic acids include saturated and unsaturated carboxylicacids. Crosslinking is not suggested.

In EP2628530 A1 crosslinking of oligocarbodiimides is described by usingone or more di- and/or polycarboxylic acids and/or their water-solublesalts as crosslinkers for the preparation of microcapsules. Neithercyclic carbonates nor curing with amine hardeners and the preparation ofhydroxyurethanes are mentioned or suggested.

It is thus a first subject matter of the present invention to provide acurable organic polymer comprising at least one acylurea unitrepresented by formula (I):

“Polymer”, as this term is used throughout this specification, isintended to also include, besides true polymers, as well dimers, trimersand/or oligomers. In other words, the “polymer”, as explainedhereinbelow, can include one or more repeating units (n).

With other words, the structural formula (I) may also be defined as anacylurea unit formed via condensation reaction of a carbodiimide and2-oxo-1,3-dioxolane-4-carboxylic acid.

The curable organic polymer comprises preferably 3 to 12, and inparticular 4 to 8 acylurea units.

A preferred embodiment of the curable organic polymer is represented bystructural formula (II):

with n being the number of repeating units within the polymer chain,

wherein n=1 to 12, and

wherein R¹ is selected from straight-chain, branched or cyclicC₁₋₁₂-alkyl groups, C₆₋₁₀-aryl groups, C₆₋₁₄-aralkyl groups, andC₆₋₁₄-alkaryl groups, and wherein

the polymer is terminated by terminal groups, which are, in each caseindependently of one another, selected from:

wherein R², R³ and R⁴ are independently of one another selected fromstraight-chain, branched or cyclic C₁₋₁₂-alkyl groups, C₆₋₁₀-arylgroups, C₆₋₁₂-aralkyl groups, C₆₋₁₂-alkaryl groups,C₁₋₄-alkoxy-C₂₋₁₂₀-(poly)(oxyalkylene) groups, polyester groups andpolycarbonate groups.

Preferred examples of R¹ are:

and combinations thereof.

Preferred meanings of R², R³ and R⁴ are e.g. methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neo-5 pentyl,n-hexyl, 2-ethyl-n-hexyl, cyclohexyl, phenyl, benzyl, (alkyl)polyethergroups (such as alkoxy-polyoxyethylene groups), (alkyl)polycarbonategroups, (alkyl)polyester groups, and combinations thereof. A mostpreferred meaning of R² is a (poly)(ethyleneoxy)alkyl group.

A second subject matter of the present invention is to provide a processfor the preparation of the curable organic polymer of the invention byreacting 2-oxo-1,3-dioxolane-4-carboxylic acid of formula (III):

with a polymer comprising at least one carbodiimide unit represented bystructural formula (IV):

—N═C═N—  (IV).

The structural formula (IV) is defined as a “carbodiimide” group, and apolymer comprising at least two carbodiimide units is defined as a“polycarbodiimide”.

Organic carbodiimides are known, their chemistry is for exampledescribed in Chemical Reviews, Vol. 53 (1953), page 145 to 166 andAngewandte Chemie 74 (1962), page 801 to 806. (Poly)carbodiimides areprepared by exposure of a basic catalyst on sterically hinderedisocyanates under CO₂ evolution. Basic catalysts can be e.g. phospholeneor phospholidine catalysts.

Polymers comprising at least one carbodiimide unit as represented informula (IV) can for example be prepared by carbodiimidisation ofisocyanates. The resulting isocyanate-terminated polymers(polycarbodiimides) can either be used directly or furtherfunctionalized by partial or complete urethane formation of the terminalisocyanate groups with alcohols or by partial or complete reaction ofthe isocyanate group with a primary or secondary amine to give an urea.Polymers comprising at least one carbodiimide unit as represented informula (IV) can also be prepared by partial reaction of diisocyanateswith alcohols followed by carbodiimidization.

Examples of such (poly)carbodiimides are described in DE 4318979 A1 andin http://www.picassian.com/Default.aspx?cms=181 (retrieved Aug. 27,2014). Such carbodiimides are for example Elastostab® H01, Elastostab®H02 (Elastogran GmbH), Picassian® XL-701, XL-702, XL-706, XL-725, XL-732(Picassian) or Desmodur® XP 2802 (Bayer AG).

The reaction of carbodiimides with acids per se is also known in theprior art, especially for the activation of carboxylic acids, a processbroadly used in peptide synthesis. Usually an O-acylurea is formed as areactive intermediate which may rearrange to a N-acylurea in a1,3-rearrangement [D. F. De Tar, R. Silverstein, J. Am. Chem. Soc. 1966,88, 1013-1030]. The reaction of bis-carbodiimides with bis-carboxylicacids has for example been used by Iwakura et al. [Polymer Letters, 6,517-522, 1968] to prepare poly(N-carbamoylamides).

Said process may suitably be carried out with a stoichiometric amount of0.5 to 2.0 molecules of 2-oxo-1,3-dioxolane-4-carboxylic acid withrespect to the carbodiimide unit of formula (IV). Preferably astoichiometric amount of 0.8 to 1.2 equivalents of2-oxo-1,3-dioxolane-4-carboxylic acid with respect to the carbodiimideunit of formula (IV) is used, in particular a stoichiometric amount of1.0 equivalents of 2-oxo-1,3-dioxolane-4-carboxylic acid percarbodiimide unit of formula (IV) is used.

When the starting polycarbodiimides are obtained from diisocyanates bythe carbodiimidization reaction as explained hereinabove, possessing—NCO end groups, additional excess of “CYCA” should preferably beprovided in order to obtain polymers according to the invention having2-oxo-1,3-dioxolane-4-carboxamide end groups.

A preferred embodiment of the process for the preparation of the curableorganic polymer of the invention is that it is performed at 20-100° C.,preferably 20-30° C. and that it is carried out in the presence of asolvent, preferably a solvent selected from acetone, THF, toluene anddioxane.

The process for the preparation of the curable organic polymer of theinvention can also be performed in the presence of a catalyst selectedfrom tertiary amines, organometallic compounds, and mixtures thereof.The tertiary amine can be selected e.g. from dimethylcyclohexylamine,4-dimethylaminopyridine (DMAP), diazabicyclooctane (DABCO), anddiazabicyclo-undecene (DBU); the organometallic compound can be selectede.g. from dibutyltin dilaurate (DBTL), a bismuth carboxylate such asbismuth octanoate or bismuth neodecanoate, a titanium or zirconiumalkoxylate or carboxylate, and the like catalysts known in the priorart.

A further subject matter of the present invention is the use of thecurable organic polymer of the invention for the preparation of a curedcomposition and for the preparation of hydroxyurethanes. Curing of thepolymer can be achieved via reaction with amines, such as at leastbifunctional amine hardeners.

Here in principle two different curing mechanisms are possible. First, acured composition can be obtained via crosslinking of the polymer-boundcyclic carbonate group with an at least bifunctional amine. Theformation of two different hydroxyurethanes is possible, namelyhydroxyurethanes with primary or secondary hydroxyl groups. In thisrespect, it has been shown that the electron-withdrawing CON groupdiverts the reaction essentially in the direction of thehydroxyurethanes with secondary hydroxyl groups since, in the event ofattack of the nucleophilic nitrogen atom, the negative charge on theoxygen atom which is closer to the COO group is better stabilized.Hydroxyurethanes with secondary hydroxyl groups have the additionaladvantage that the back-reaction is hindered.

Second, an attack of the amine at the acylurea group is also conceivableto a lower extent, leading to the formation of a crosslinked network viahydroxyurethane and urea linkages. The cleavage reaction of the acylureadoes not essentially reduce the crosslinking density as the second aminogroup can either react with a cyclic carbonate or with a diimide toachieve crosslinking. Thus, in both cases a dense network is formed. Inthe latter case an excess of amine, preferably an amine to cycliccarbonate ratio of 1:2 can further increase the crosslinking density.

Suitable amines are primary and secondary amines with alkyl groups, arylgroups, aralkyl groups, and alkylaryl groups. Primary amines react muchquicker than secondary amines; aliphatic amines react more quickly thanaromatic amines. As regards the relative reactivities of differentamines, compare C. Diakoumakos, D. Kotzev, Non-Isocyanate-BasedPolyurethanes Derived upon the Reaction of Amines with CyclocarbonateResins, Macromol. Symp., 216, 37-46 (2004), in particular scheme 4 on p.45. All of the amines specified therein and standard amine hardenersthat are known to a person skilled in the art are suitable for carryingout the present invention. Relatively high molecular weight amines suchas e.g. Jeffamine® from Huntsman Corp., polyether amines from BASF SE orpolyethyleneimines such as Lupasol® from BASF SE are also suitable.

Theoretically, curing can also be achieved with other hardeners bearingnucleophilic groups such as OH or SH groups. Appropriate hardeners couldbe at least bifunctional alcohols or thiols.

One advantage of the organic polymer comprising at least one acylureagroup of the invention lies in the high density of functional groups andthus the ability to achieve a high crosslinking density when curing withan at least bifunctional hardener such as an at least bifunctional amineis performed. Consequently hard and strong materials can be obtainedwith this type of reaction.

Moreover, when producing polyhydroxyurethane systems which are based onthe organic polymer comprising at least one acylurea group of theinvention, bubble formation as a result of formed CO₂ may not arise,even in the presence of moisture. Consequently, largely pore- andbubble-free coatings are possible, which is sometimes problematic forclassic polyurethane systems. Additionally, systems based on the organicpolymer of the invention can be dissolved or dispersed in water which isdifficult for isocyanate based systems. The possibility to usewaterborne systems enables the use of the polymer of the invention in alow viscous and VOC-free dosage-form. Furthermore, the thermal stabilityof such polyhydroxyurethane systems is also higher than the stability ofclassic polyurethane systems.

The present invention is now illustrated in more detail by reference tothe examples hereinbelow.

EXAMPLES Example 1 Preparation of a TDI-carbodiimide and SubsequentReaction with CYCA

34.83 g TDI (0.2 mol) was dissolved in 66 ml hexane and 0.25 g DMPO(Phospholene oxide, Lubio Polykat® 1, Schäfer-Additivsysteme GmbH) wasadded. The reaction mixture was stirred at ambient temperature for 12 h,and a white precipitate formed. The solid product was filtered off,washed with petrol ether and recrystallized from hexane.

¹H-NMR (400 MHz, CDCl₃): δ=7.12-6.86 (m, 6H, Ar), 2.29 (s, 6H, CH₃) ppm.

IR (v, cm⁻¹): 2361 (w), 2344 (w), 2273 (s, NCO), 2131 (s, diimide), 2098(s, diimide), 1717 (w), 1600 (s), 1562 (m), 1512 (m), 1477 (s), 1287(w), 1224 (w), 1196 (m), 1145 (w), 1073 (m), 993 (m), 917 (m), 887 (s),823 (s), 751 (w), 718 (m), 591 (s), 548 (s).

2.25 g of the obtained TDI-carbodiimide (7.4 mmol) was dissolved in 60ml dry THF and 2.93 g (22.2 mmol) 2-oxo-1,3-dioxolane-4-carboxylic acid(CYCA) was added. The reaction mixture was stirred at ambienttemperature until the carbodiimide was reacted completely (12 h, IRcontrol). Afterwards, 0.04 g DMAP (4-dimethylamino pyridine, 0.3 mmol)were added and the reaction mixture was heated to 65° C. until theTDI-carbodiimide was completely reacted (12 h). During this period awhite precipitate formed which was filtered off and dried in vacuo. Thesolid product was obtained as a white powder in quantitative yield.

IR (v, cm⁻¹): 3356 (bw), 2975 (m), 2870 (m), 2275 (w), 1817 (s,cyclocarbonate), 1704 (s), 1592 (m), 1536 (s), 1451 (m), 1413 (w), 1385(w), 1220 (m), 1155 (s), 1058 (s), 899 (m), 815 (w), 766 (w), 656 (m),532 (w).

Example 2 Reaction of TMXDI-carbodiimides with CYCA

a) 12.5 g Elastostab® H02 (NCO-terminated TMXDI-carbodiimide of BASF, 7%Isocyanate, 14% Carbodiimide) was dissolved in 80 g dry acetone and 8.53g (0.065 mol, excess) 2-oxo-1,3-dioxolane-4-carboxylic acid (CYCA) wasadded. The reaction mixture was stirred at ambient temperature until thecarbodiimide was completely reacted (12 h, IR control). Afterwards 0.16g DMAP (1.3 mmol) was added, and the reaction mixture was heated to 65°C. until the TMXDI-carbodiimide was completely reacted (12 h). Thesolvent was evaporated and the product was obtained as white powder inquantitative yield.

b) 277 g Elastostab® H01 (polyether-terminated TMXDI-carbodiimide ofBASF, 7% Carbodiimide) was dissolved in 1 l dry acetone and 64 g (0.49mol) 2-oxo-1,3-dioxolane-4-carboxylic acid (CYCA) was added. Thereaction mixture was stirred at ambient temperature until thecarbodiimide was completely reacted (12 h, IR control). The solvent wasevaporated, and the product was obtained as white powder in quantitativeyield.

IR (v, cm⁻¹): 3310 (bw), 2974 (m), 2862 (m), 1822 (m, cyclocarbonate),1710 (m), 1693 (m), 1521 (w), 1460 (w), 1386 (w), 1252 (m), 1149 (m),1065 (s), 907 (s), 799 (w), 766 (w), 708 (w), 655 (w), 499 (w).

Example 3 Reaction of IPDI-carbodiimide with CYCA

28.39 g IPDI-carbodiimide (of BASF, 6.8% diimide content, 60% solutionin Proglyde® DMM,) was dissolved in 100 ml dry THF, and 3.74 g (0.18mol) 2-oxo-1,3-dioxolane-4-carboxylic acid (CYCA) was added. Thereaction mixture was stirred at ambient temperature until thecarbodiimide was completely reacted (12 h, IR control). The solvent wasevaporated and the product was obtained as a viscous yellow oil inquantitative yield.

IR (v, cm⁻¹): 2973 (m), 2862 (m), 2122 (w), 1823 (m, cyclocarbonate),1692 (m), 1539 (w), 1460 (m), 1366 (w), 1245 (w), 1066 (s), 907 (m), 766(w), 655 (w).

Example 4 Curing of Acylurea-Based Cyclocarbonate Binders

The reaction products of Examples 2a and 2b were cured with differentbi/tri-functional amine hardeners. The respective reaction products,amine hardeners, amounts (mol), cyclocarbonate (“Cyc”):amine ratio, andthe curing behavior are given in Table 1 hereinbelow.

TABLE 1 Binder/Amine Amount “Cyc”:Amine Curing Behavior 1 Ex. 2a, 60%solution in THF 0.005 1:1 Exothermic, fast curing, potlife IPDA 0.005 10min, brittle, tack-free 2 Ex. 2a, 60% solution in THF 0.005 1:1 Veryexothermic, fast curing, DYTEK ® EP diamin 0.005 potlife 10 min,brittle, tack-free 3 Ex. 2a, 60% solution in THF 0.005 1:1 Exothermic,fast curing, potlife 1,3-Diamino-2,2- 0.005 10 min, brittle, tack-freedimethylpropan 4 Ex. 2a, 60% solution in THF 0.005 1:1 Exothermic, fastcuring, potlife Diethylentriamin 0.005 10 min, brittle, tack-free 5 Ex.2a, 60% solution in THF 0.005 1:1 Gelling, no complete curing Jeffamin D400 0.005 6 Ex. 2a, 60% solution in THF 0.005 1:1 Potlife 5 min, tackyPolyetheramin T 403 0.005 7 Ex. 2a, 60% solution in THF 0.005 1:1Exothermic, fast curing, potlife 1,3-Cyclohexanbis(methylamin) 0.005 10min, brittle, tack-free 8 Ex. 2b, 70% solution in H₂O 0.005 1:1 Tacky,soft and elastic IPDA 0.005 9 Ex. 2b, 70% solution in H₂O 0.005 1:2 Hardand brittle, tack-free, IPDA 0.010 completely cured 10 Ex. 2b, 70%solution in H₂O 0.008 1:2 Cured, tacky TMD 0.016 11 Ex. 2b, 70% solutionin H₂O 0.003 — No curing Without Amine —

Curing of acylurea-based cyclocarbonate binders can be observed withvarious amines. Best results, i.e. tack-free, stable and hard films withgood mechanical properties were obtained with the modified Elastostab®H01 system (i.e. Ex. 2a) with an excess of IPDA.

1. A curable organic polymer comprising at least one acylurea unitrepresented by structural formula (I):


2. The polymer of claim 1, comprising 3 to 12 acylurea units.
 3. Thepolymer of claim 1, characterized in that the polymer is represented bystructural formula (II):

with n=1 to 12 and wherein R¹ is selected from straight-chain, branchedor cyclic C₁₋₁₂-alkyl groups, C₆₋₁₀-aryl groups, C₆₋₁₄-aralkyl groups,and C₆₋₁₄-alkaryl groups and in that the polymer is terminated byterminal groups, which are, in each case independently of one another,selected from:

wherein R², R³ and R⁴ are independently of one another selected fromstraight-chain, branched or cyclic C₁₋₁₂-alkyl groups, C₆₋₁₀-arylgroups, C₆₋₁₂-aralkyl groups, C₆₋₁₂-alkaryl groups,C₁₋₄-alkoxy-C₂₋₁₂₀-(poly)(oxyalkylene) groups, polyester groups andpolycarbonate groups.
 4. The polymer of claim 3, characterized in thatR² is an alkoxy-polyoxyethylene group with a molecular weight of 76 to2000.
 5. A process for the preparation of a curable organic polymer asdefined in claim 1, characterized in that2-oxo-1,3-dioxolane-4-carboxylic acid of formula (III):

is reacted with a polymer comprising at least one carbodiimide unitrepresented by structural formula (IV):—N═C═N—  (IV).
 6. The process of claim 5, characterized in that 0.5 to2.0 equivalents of 2-oxo-1,3-dioxolane-4-carboxylic acid of formula(III) are used per carbodiimide unit of formula (IV).
 7. The process ofclaim 5, characterized in that the reaction is performed at 20-100° C.8. The process of claim 5, characterized in that the reaction is carriedout in the presence of a solvent.
 9. The process of claim 5,characterized in that the reaction is performed in the presence of acatalyst selected from tertiary amines, organometallic compounds, andmixtures thereof.
 10. A process comprising utilizing the polymer asdefined in claim 1 comprising curing the polymer for the preparation ofa cured composition.
 11. The process of claim 10, characterized in thatthe polymer is cured by reaction with an at least bifunctional amine.12. The process of claim 5, characterized in that the reaction isperformed at 20-30° C.
 13. The process of claims 5, characterized inthat the reaction is carried out in the presence of a solvent selectedfrom acetone, THF, toluene and dioxane.
 14. The polymer of claim 1,comprising 4 to 8 acylurea units.